function F=Rand_F(mu_F,sigma,NP)
    F=mu_F+sigma*tan(pi*(rand(1,NP)-1/2));
    index1=find(F>1);
    index2=find(F<0);
    [~,n1]=size(index1);
    [~,n2]=size(index2);
    while n1~=0||n2~=0
        if n1~=0
            F(index1)=mu_F+sigma*tan(pi*(rand(1,n1)-1/2));
        end
        if n2~=0
            F(index2)=mu_F+sigma*tan(pi*(rand(1,n2)-1/2));
        end
        index1=find(F>1);
        index2=find(F<0);
        [~,n1]=size(index1);
        [~,n2]=size(index2);
    end 
end